Magnesium base alloy



PatentedJuly 26, 1938 OFFICE John Gann., Midland, Mich., assignor to The Dow Chemical Compan poration of Michigan y, Midland, Mich a cor- No Drawing. Original application August 2, 1937,

Serial No. 156,941. Divided and this application February 3,1938, Serial No. 188,461

4 Claims. (01. 15-103) The present invention relates to magnesium alloys. and more particularly to those in which magnesium is the predominant constituent.

A large number of magnesium alloys have been 5 developed and many of them have been used commercially. While certain of these alloys have tensile strengths-that are satisfactory for a wide variety of uses, their yield strengths are often so low that articles'made from such alloys will deform readily and assume a large permanent set at a stress considerably below the stress corresponding to'the ultimate tensile strength.

The principal object of my invention is to produce magnesium alloys having improved physical properties. A more specific object is to produce magnesium alloys having improved ratios of yield strength to'tensile strength. Other objects and advantages will appear as the description proceeds. 5

This invention is based on thediscovery that the -magnesium-aluminumcadmium alloys, as

described in"United States Patent No. 1,729,339,

may be improved to awery marked extent by the addition of relatively small amounts of lead and that this alloy may be still further improved by the addition of relatively small'amounts 01 at least one of the metals selected from the group, tin

and zinc. I have likewise discovered that maximum property improvement is obtained when 9 these alloys are subjected to the well known methods of solution heat treatment and aging. I have found that these advantages occur when 1 approximately 0.5 to 10 per cent of lead are added to the known magnesium-aluminum-cadmium 35 alloy containing 1 to 12 per cent of aluminum and 1 to 10 per cent of cadmium, thereby producing my new magnesium-aluminum-cadmium-lead alloy. I have likewise discovered that the prop 40 erties of this magnesium-aluininum-cadmiumlead alloy may be improved by adding approximately 0.5 to 8 per cent of at least one of the metals selected from the group'of relatively low melting-point metals, tin and zinc.

Thefollowing tables give specific examples which illustrate, the improvement in yield strength and in the ratioot yield strength to tensile strength of my new alloy as compared to the known magnesium-aluminum-cadmiumj a1- 50 loys. .I have likewise found thatthe increase in yield strength and in the yield strength to tensile strength ratio, as given in these tables, is accompanied by an improvementinBrinell hardness amounting to approximately 25 per cent for the as cast alloys, 35 per cent for the solution heat treated alloys, and 55 per cent for the solution heat treated and aged alloys.

" Cast alloys Nominal composition 5 Ratio 5 53? Yield Tensile yield 5 strength, strength, strength a lb./sq.in. lb./sq. in. to tensile Al ca Pb s11 Zn Strength 4 4 7,400 21,100 4 v 4 2 0,300 23,500 .31 0 4 2 10,500 23,000 .36 15 6 4 2 13,100 22,400 .58 5 4 2 2 13,200 21,300 .43 0 4 2 0 15,300 24,500 .03 s 2 12,000 V .43 a z 1 1 13.2 2 I .12

Solution 5m mm a 6 4 2 2 13,100 35,000 .31 6 4 2 0 15,000 a ,100 .53 s 2 11,500 32,000 .36 a 2 1 4 15,300 32,500 .41 s 2 1 4 10,300 20,300 .55 s 2 .1 5 4 11,200 28,800 .60 4 0 0 2 3 12,400 21,200 .45

Solution heat treated and and alloyt 2 a' 0,100 000 .23 2 s 10 3,100 $1300 .31 40 2 s 10 2 10,200 25,000 .41

4 v4 1,200 20,500 .25 4 4 4 2 1,100 20,000 .21 6 4 2 10,100 31,100 .32 0 4 2 0 3.: 13,000. 30,300 .45 .0 4 2--.- 2 13,000 34,300 .52v 0- 4 2 0 23,300 23,000 .32 s 2 14,200 32,000 .44 s 2 1 4 24,200 35,400 .55 s 2 1 4 24,500 33,600 .10 a 2 .1 5 4 23,300 32,200 .12 4 0; 0 -.2 3 10,400 30,000 .55 a

(The specific proportions of each metal to be employed in these new alloys depends on the use for which the alloy is intended. In general, I

prefer to use alloys containing more than per cent of magnesium and less than 20 per cent of total added metals, but where the alloy is to be used for the production of wrought shapes generally, suitable'compositions are those containing more than 90 per cent of magnesium and less than 10 per cent of total added metals. For the production of castings, the alloy should preferably contain 85 to 92 per cent of magnesium and the various alloying ingredients in the following proportions: 4 to 10 per cent of aluminum, 2 to 8 per cent of cadmium, 1 to 6 per cent of lead, 1 to 6 "per cent of tin, and 1 to 4 per cent of zinc. For

cadmium, 0.5 to 2 per cent of lead, 0.5 to 3 per cent of tin, and 0.5 to 2,per cent of cine. If the alloy is to be fabricated by rolling rather than by extrusion or forging, the percentage of aluminum should preferably lie within the range of 1 to 5 per cent. I

My new polynary alloys may be prepared by the methods usually employed for melting and alloying metals with magnesium, such as adding the respective alloying metals singly or jointly to a bath of molten magnesium protected from oxidation by a cover of fluid flux. The solution-heat treatment forthe zinc-free alloys may consist in heating the material for 20 hours at'430 C., followed by air cooling, or, when zinc is present in the alloy, 12 hours at 320 C. plus 16 hours at 420 C., followed by air cooling. The aging treatment consists of approximately 16 hours heating at 175 C., subsequent to the above solution heat treatment. Plastic deformation operations, such as extruding, forging, and rolling are best conducted at temperatures between 300 and 400" This application is a division of my co-pending 5 application Serial No. 156,941, filed August 2, 1937.

Other modes of applying the principle of my invention may be employed instead of those explained, change being madeas regards the 'in- Y gradients and the steps herein disclosed, provided those stated by any of the following claims ortheir equivalent be employed. I particularly point out and distinctly claim as my invention:- 1. A magne'si -base alloy containing about 1 to 12 per cent of aluminum, about 1 to 10 per cent of cadmium, about 0.5 to 10 per cent of lead, and about 0.5 to 8' per cent of zinc, the balance being magnesium. 20

2. A magnesium-base alloy containing about 4 to 10 per cent of aluminum, about 2 to 8 per cent of cadmium, about 1 to 6 per cent of lead, and about 1 to 4 per cent of zinc, the balance being magnesium. v r

3. A magnesium-base alloy containing about 1 to 8 per cent of aluminum, about 1 to 3 per cent of cadmium, about 0.5 to 2 per cent of lead, and about 0.5 to 2 per cent of zinc, the balance being magnesium.

4. A magnesium-basealloy containing about 6 per cent of aluminum, 4 per cent of'cadmium, 2 per cent of lead, and 2 per cent of zinc, the balance being magnesium.

- JOHN A. GANN. 

